FACT SHEET: Preimplantation Genetic Diagnosis (PGD)
& Preimplantation Genetic Screening (PGS)
What is PGD/PGS?
Preimplantation Genetic Diagnosis (PGD) and Preimplantation Genetic Screening (PGS) are elective tests that can be added to an IVF cycle. These tests screen for a number of genetic abnormalities and help to ensure only healthy embryos are transferred, which have the best chance for a successful pregnancy and healthy baby. Your doctor will determine if you are a good candidate for PGD/PGS based on your medical history and age.
What is involved with a PGD/PGS cycle?
The PGD/PGS process begins with egg retrieval and embryo culture as part of IVF. Once the retrieved egg has been fertilized in our laboratory, the embryo is allowed to develop for five days. Our embryologist biopsies 3-4 of the trophectoderm cells (a layer of cells that will eventually become your baby’s placenta), which are then analyzed in the lab for chromosomal abnormalities. The testing takes about 7 days to complete.
How are the cells biopsied? Is it safe?
Under a high-power microscope and with the use of sophisticated, hydraulically-operated, ultrafine microscopic glass instruments, our experienced embryology team stabilizes the embryo and makes a small hole in the shell surrounding the embryo. This state-of-the-art technique, called "assisted hatching", involves using a special laser to assist the embryo's natural hatching process, creating a small window through which the cells emerge. The small (3-4 cell) sample is quickly microsurgically shaved off without significantly affecting the embryo. The embryo is then frozen, essentially paused in its development, while the pre-implantation genetic testing takes place at a specialized lab. This freezing process is similar to freezing extra embryos during IVF and is completely safe.
What’s the difference between PGD and PGS?
Many people these two terms interchangeably, but here is the difference:
• PGD is most commonly used when a couple is looking to diagnose or screen for a specific genetic disease, such as when the parents are carriers of Tay-Sachs or another single-gene mutation.
• PGS, on the other hand, is a more generalized test in which the embryo is screened for the number of chromosomes. Abnormalities in the number of chromosomes (aneuploidy) can lead to failed IVF cycles, miscarriages, and/or birth defects.